1. Field of the Invention
The present invention relates to an image forming apparatus for recording images on a sheet-shaped recording medium such as paper cut to a given size, and a paper feeding apparatus for piling up image recording sheets of paper on one another to store the image recording sheets of paper therein and also for feeding out the image recording sheets of paper one by one therefrom.
2. Description of the Related Art
An image forming apparatus such as a copying machine, a printer and a facsimile includes various types such as an electrophotographic type, an ink jet type and a heat transfer type; and, in most of them, images such as letters and pictures are formed on paper which is cut to a given size.
For example, in the ink jet type and heat transfer type, the images are formed on the paper in accordance with digital signals. Also, in the electrophotographic type and electrostatic recording type, toners are applied onto electrostatic latent images carried on an image carrier element to thereby form toner images there, and the toner images are then transferred to and fixed on the paper.
The sheets of paper, on which images are to be formed, are generally piled up on top of each other and stored in a paper feeding apparatus disposed within the image forming apparatus and the thus stored sheets of paper are then supplied sequentially one by one from the paper feeding apparatus.
The sheets of paper to be stored within the paper feeding apparatus must be replenished properly. In order to be able to facilitate this paper replenishment, there is used a paper tray which can be mounted onto and removed from the main body of the image forming apparatus; that is, the sheets of paper are replenished into the paper tray and stored in the paper tray. In some cases, only one paper tray is disposed for one image forming apparatus; and, in most cases, two or more cassettes (paper trays) are used in combination in order to be able to select sheets of paper of different sizes and apply images onto the selected paper. And, in some other cases, in combination with the two or more paper trays, there is disposed a hand-held tray which is convenient when various sheets of paper having different sizes are used arbitrarily.
A mechanism, which is used to take out the sheets of paper one by one from the paper tray or hand-held tray and feed them one by one to a position where images can be given, is generally structured as shown in FIGS. 8A and 8B.
Specifically, FIG. 8A shows a structure of a type in which a function to feed out the sheets of paper and a function to prevent two or more sheets of paper from being fed together in a superimposed manner are divided from each other; and, this type of structure comprises a paper feed roller 101 which can be contacted with the upper surface of paper 104 stored within a paper tray and can be rotated to thereby feed out the top-layer sheet of paper from the paper tray, a handling roller 102 for delivering the thus fed-out paper while preventing two or more sheets of paper from being fed together in a superimposed manner, and a handling member (pad) 103 which is formed of material showing large friction and can be contacted with the handling roller 102 to thereby separate superimposedly-fed sheets of paper from each other.
In this mechanism, the paper 104, which has been fed out from the paper tray by the paper feed roller 101, is passed through the contact position between the handling roller 102 and handling member 103 and is then delivered to an image applying position. And, in case where two or more sheets of paper are taken out from the paper tray while they are superimposed on top of each other, at the time when the lower surface of the paper is contacted with the handling member 103, the friction between the paper 104 and handling member 103 becomes larger than the friction between the superimposed sheets of paper, so that the sheet of paper on the lower side is separated from the sheet of paper on the upper side and thus only the sheet of paper on the upper side is delivered to the image applying position.
Now, FIG. 8B shows a structure of another type in which a paper feed roller has a function to feed out the sheets of paper from the paper tray and a function to prevent two or more sheets of paper from being fed together in a superimposed manner. In this type of structure, a paper feed roller 111 is contacted with the upper surface of paper 113 stored in a paper tray and, at the same time, a handling member 112 is contacted with the rotation-direction downstream side of the paper feed roller In this type of mechanism, similarly to the above type of mechanism, the paper can be fed out from the paper tray and, while the handling member 112 prevents two or more sheets of paper from being fed together in a superimposed manner, only a sheet of paper can be delivered to the image applying position. In this type, since the contact portion of the paper 113 and the contact portion of the handling member 112 are set on the peripheral surface of the paper feed roller 111, the diameter of the paper feed roller 111 must be set rather large. In spite of this, however, there can be obtained an advantage that the paper feed mechanism can be simplified in structure and thus the manufacturing cost thereof can be reduced.
On the other hand, the paper tray is classified into two types according to the removing directions thereof, while the two types of paper trays are selectively used depending on the types of the paper feed mechanisms. That is, when the paper tray is set, the paper feed mechanism is situated in the vicinity of the end portion of the paper tray and feeds out the sheets of paper substantially in the horizontal direction from the end portion of the paper tray. In this case, there are two types of paper trays: specifically, in one type, the paper tray can be removed from an image forming apparatus by pulling the paper tray in the same direction as a direction in which the paper is fed out from the paper tray; and, in the other type, the paper tray can be removed by pulling the same in the opposite direction to the above-mentioned paper feed-out direction.
An image forming apparatus of a type that a paper tray is removed in the same direction as the paper feed-out direction is disclosed in, for example, JP-A-4-247469 and JP-B-7-40169.
Also, an image forming apparatus of a type that a paper tray is removed in the opposite direction to the paper feed-out direction has such a structure as shown in FIG. 9.
In this apparatus, paper trays 121, 122 can be mounted into and removed from the apparatus through the front surface thereof; and, paper fed out from the reapportion of the apparatus is passed through a delivery passage 123 and is then delivered to a portion 124 where an image is transferred.
As a mechanism for operating a handling member when removing a paper tray from the main body of the image forming apparatus, there are two different types. That is, in one type of mechanism, the handling member is supported on the apparatus main body side and thus it is separated from the paper tray; and, even in case where the paper tray is pulled out from the apparatus main body, the handling member is still left within the apparatus. On the other hand, in the other type of mechanism, the handling member is mounted on the paper tray and thus the handling member is taken out from the apparatus main body simultaneously when the paper tray is pulled out.
Also, as a mechanism for bringing sheets of paper piled up within a form tray into contact with a paper feed roller, there are available various types.
The sheets of paper to be stored within the paper tray varies in quantity as they are replenished or consumed but the upper surface of the top-layer sheet of paper must be always contacted with the paper feed roller. In view of this, there are employed many mechanisms structured such that the paper feed roller or the piled-up sheets of paper can be energized by springs or other similar means. Of these mechanisms, a mechanism, in which the sheets of paper can be contacted with the paper feed roller in linking with the mounting and removing operation of the paper tray, is simplified in structure to thereby be able to provide many advantages. Referring here to the specific structure of this mechanism, within the paper tray, there is disposed a paper carrier plate which can be moved up and down and, in linking with the paper tray mounting operation, the paper carrier plate is moved up and guided to thereby be able to bring the upper surface of the paper into contact with the paper feed roller.
However, in the above-mentioned conventional image forming apparatus or paper feeding apparatus, there are still found the following several drawbacks that are tone improved or solved.
That is, in the structure comprising two or more paper trays each formed as a cassette that can be mounted into and removed from the apparatus main body, or in the structure comprising one or more mountable and removable paper tray(s) and a hand-held paper tray for placing sheets of paper onto the paper placing portion of the apparatus main body by hand, as in the apparatus shown in FIG. 9, generally, the paper trays and hand-held paper tray are disposed respectively on the upper and lower sides in the vertical direction. In the apparatus in which the direction to feed out the paper from the paper trays is the same as the direction to pull out the cassettes from the apparatus main body, there may be employed a structure in which the hand-held paper tray is not arranged above or below the paper trays in the vertical direction. On the other hand, in the apparatus in which the paper feed-out direction is opposite to the paper tray pull-out direction, as shown in FIG. 9, from the viewpoint of the arrangement of a paper delivery passage as well as the stable installation of the paper trays, it is most reasonable that the paper trays and hand-held paper tray are respectively arranged in the vertical direction.
However, in the thus structured apparatus, there arises a problem that the vertically piled-up arrangement of the sheets of paper increases the height of the apparatus. Especially, in case where a single paper feed roller has not only a function to feed out the paper from the paper trays but also a function to prevent two or more sheets of paper from being fed together in a superimposed manner, the diameter of the paper feed roller becomes larger, which worsens the above problem to a great extent.
On the other hand, as in an apparatus which is disclosed in JP-A-59-190129, there is also known a structure in which an upper-stage paper tray is set at a position with drawn backwardly of a lower-stage paper tray. However, in this apparatus, the paper feed starting positions in the respective paper trays are distant from each other, whereby the delivery passages of the sheets of paper fed out from these paper trays are complicated in structure. This causes an obstacle to reduction in the manufacturing cost of the apparatus.
Also, as a second problem, in the structure that the paper tray is pulled out from the apparatus may body in the opposite direction to the paper feed-out direction, in case where the handling member is mounted on the paper tray, the paper feed roller supported on the apparatus main body interferes with the handling member, which makes it impossible to pull out the paper tray. That is, in FIG. 8B, when trying to move the handling member 112 mounted on the paper tray together with the paper tray in a direction of an arrow mark C, the paper feed roller 111 provides an obstacle to such movement, thereby making it impossible to pull out the paper tray.
On the other hand, in case where the handling member is supported on the apparatus main body side, there can be avoided the obstacle to the paper tray pull-out operation but, when the paper tray is pulled out, in case where one or more sheets of paper having reached the handling member and prevented against superimposedly simultaneous feeding are present on the handling member, such sheet(s) of paper are left within the apparatus main body. Also, in the Japanese Patent No. 2584849, there is disclosed a mechanism which can retreat the handling member from the paper feed roller at the same time when the paper tray is pulled out. However, such mechanism is complicated, which results in the increased manufacturing cost of the apparatus.
As a third problem, in case where two or more paper trays are arranged in the vertical direction and the distance between these paper trays is narrowed so as to minimize the height of the apparatus, it is difficult to provide a mechanism which is used to raise the paper carrier plate such that the sheets of paper stored in the paper trays can be contacted with the paper feed roller. In other words, the limited vertical dimension makes it impossible to provide a paper tray storing portion on the bottom portion of the apparatus; that is, the paper tray storing portion must be provided on the side portion of the apparatus. However, in this case, it requires a large force to raise a large number of piled-up sheets of paper and energize the paper feed roller and, therefore, the paper carrier plate must be guided by a member having sufficient strength. Also, it is necessary to employ a structure in which members mounted on the apparatus main body side can be prevented from interfering with the paper tray. This requires a new improvement in a mechanism for raising the paper carrier plate.
The present invention aims at eliminating the above-mentioned drawbacks found in the conventional image forming apparatus and paper feeding apparatus. Accordingly, it is an object of the invention to minimize the area to be occupied by a paper feeding apparatus and simplify the structures of mountable and removable paper trays and their attendant components. And, in more particular, it is an object of the invention to provide an image forming apparatus or a paper feeding apparatus including two or more paper trays in which the height of the apparatus can be minimized and the paper delivery function of the apparatus can be simplified to thereby reduce the manufacturing cost of the apparatus. And, it is another object of the invention to provide, in the above image forming apparatus or paper feeding apparatus, a structure for pulling out the paper trays in the opposite direction to the feed-out direction of sheets of paper stored in the paper trays, in which a handling member to be contacted with a paper feed roller can be prevented from interfering with the paper feed roller when the paper trays are pulled out. Further, it is still another object of the invention to provide, in the above image forming apparatus or paper feeding apparatus, a simple mechanism which is capable of energizing the sheets of paper stored in the paper trays to thereby bring the same into close contact with the paper feed roller.
In attaining the above objects, according to the invention, there is provided a paper feeding apparatus, comprising: at least two paper trays disposed respectively on the upper and lower sides in the vertical direction; a first paper feed roller contactable with sheets of paper piled up and stored in the upper-side paper tray of the vertically disposed paper trays to thereby feed out the sheets of paper one by one therefrom; a second paper feed roller contactable with sheets of paper piled up and stored in the lower-side paper tray of the vertically disposed paper trays to thereby feed out the sheets of paper one by one therefrom, wherein the first paper feed roller is disposed backwardly of and obliquely upwardly of the second paper feed roller with respect to a direction to feed out the sheets of paper.
The above-mentioned term xe2x80x9ca direction to feed out the sheets of paper (paper feed-out direction)xe2x80x9d means simply a direction on a horizontal line and thus, even in case where the sheets of paper are delivered obliquely upwardly immediately after they are fed out from the paper tray, the position of the second paper feed roller is not to be changed.
By disposing the first and second paper feed rollers in the above-mentioned manner, not only the two paper feed rollers can be respectively contacted with the end portions of the upper surfaces of the sheets of paper stored in the paper trays to thereby be able to feed out the sheets of paper from the paper trays, but also the two paper feed rollers can be positioned nearer to each other than the conventional paper feeding apparatus. And, the upper-side paper tray is positioned backwardly of the second paper feed roller and also can be arranged adjacently to the lower-side paper tray when compared with the conventional paper feeding apparatus. Therefore, the height of a space to be occupied by the paper trays and paper feed rollers can be reduced.
Also, sheets of paper, which are fed out by the thus arranged two paper feed rollers, can be fed into the same paper delivery roller. That is, since the two paper feed rollers are disposed near to each other and thus the positions where the sheets of paper are fed out are made nearer to each other, two paper delivery passages from the two paper feed rollers can be made to meet each other at a position near to the two paper feed rollers; and, therefore, the sheets of paper can be fed directly into the same paper delivery roller without providing delivery rollers separately in the paper delivery passages extending from the paper trays to the meeting position. With use of this structure, the paper delivery passage can be simplified in structure and thus the manufacturing cost of the paper feeding apparatus can be reduced.
On the other hand, the upper-side paper tray is disposed backwardly of and adjacently to the second paper feed roller with respect to the paper feed-out direction, and the first paper feed roller is disposed backwardly of and obliquely upwardly of the second paper feed roller, whereby the sheets of paper fed out by the first paper feed roller are allowed to pass through between the first and second paper feed rollers.
In case where the paper trays and paper feed rollers are arranged in this manner, the second paper feed roller and the upper-side paper tray can be arranged side by side at the same height position in the horizontal direction, thereby being able to reduce the height of the range to be occupied by the paper trays and paper feed rollers. And, the sheets of paper fed out from the upper- and lower-side paper trays can be delivered along the lower and upper surfaces of the second paper feed roller and the two delivery passages, can be made to meet each other in front of the second paper feed roller. Therefore, the delivery passage of the sheets of paper can be simplified in structure.
Also, when the first paper feed roller is disposed backwardly of and obliquely upwardly of the second paper feed roller with respect to the paper feed-out direction, preferably, these two paper feed rollers may be set at mutually adjacent positions and, where their radii are respectively expressed as R1 and R2, the centers of the two paper feed rollers may be spaced from each other by a distance equal to or more than R1 or R2 and equal to or less than (R1+R2) in the horizontal direction, or by a distance equal to or more than R1 or R2 and equal to or less than (R1+R2) in the vertical direction.
With use of this arrangement, the area to be occupied by the paper trays and paper feed rollers can be minimized in the horizontal direction and/or in the vertical direction. And, the sizes and positions of the paper trays can be set in such a manner that the end portion of the upper-side paper tray can be stored in an area the three sides of which are enclosed by the lower-side paper tray, second paper feed roller and first paper feed roller disposed obliquely upwardly of the second paper feed roller; that is, the space can be used reasonably and thus the area to be occupied by the paper feeding apparatus can be reduced.
On the other hand, the first paper feed roller is disposed obliquely upwardly of and adjacently to the second paper feed roller with respect to the paper feed-out direction and the height of the upper-side paper tray is set smaller than the diameter of the second paper feed roller, whereby the upper-side paper tray can be disposed backwardly of the second paper feed roller such that they are situated side by side in the horizontal direction. This can minimize the area to be occupied by the paper feed rollers and paper trays.
In the above-structured paper feeding apparatus or image forming apparatus, the first or second paper feed roller may be formed as a semicircular-shaped roller with the peripheral surface thereof cut away in part, and the first or second paper feed roller may be structured such that, while it is rotated once to thereby allow the other remaining arc-shaped portion thereof than the partially-cutaway portion to feed the sheets of paper, it feeds the sheets of paper into the common form delivery roller capable of delivering both of the sheets of paper to be fed out from the first and second paper feed rollers.
The above-mentioned semicircular-shaped roller is able to deliver the sheets of paper intermittently with a simple structure, while the deliverable length of paper is limited to the remaining peripheral length except for the cut-away portion. However, by arranging the paper feed rollers and paper trays in the above-mentioned manner, even in case where the diameters of the paper feed rollers are set large, the area to be occupied by them can be reduced. And, by setting large the diameters of the paper feed rollers, within the range that the paper feed rollers can deliver the sheets of paper, there can be disposed a common paper delivery roller which is capable of delivering the sheets of paper respectively fed out from the two paper trays, thereby being able to simplify a paper delivery mechanism.
In the above-mentioned paper feeding apparatus or in the above-mentioned image forming apparatus using such paper feeding apparatus, the paper tray used may be formed in a cassette which can be mounted into and removed from the apparatus, or may be formed as a hand-held paper tray which allows paper having an arbitrary size to be easily inserted from externally of the apparatus.
Also, with respect to the paper tray formed as a mountable and removable cassette, there can be employed the following structure:
That is, a paper feeding apparatus comprises: a paper tray in which sheets of paper can be piled up and stored; a paper feed roller contactable with the upper surfaces of the sheets of paper stored in the form tray to thereby feed out the forms one by one from the paper tray; and, a handling member, on the paper-feed-out-direction downstream side of a position at which the paper feed roller can be contacted with the sheets of paper within the paper tray, contactable with the peripheral surface of the paper feed roller to thereby prevent two or more sheets of paper from being delivered together in a superimposed manner, wherein the paper tray can be removed from the main body of the paper feeding apparatus supporting the paper feed roller by pulling out the same in the opposite direction to the paper feed-out direction. And, the present handling member is mounted on the paper tray and can be made to retreat from the surface of the paper feed roller when the paper tray is pulled out from the paper feeding apparatus main body.
For a mechanism which is used to retreat the handling member, for example, there can be employed the following structure: that is, the handling member is disposed on the other end side of a holder having one end rotatably mounted on the form tray, and the position of the holder can be restricted such that the handling member can be contacted with the paper feed roller or the handling member can be made to retreat from the paper feed roller as the paper tray is mounted or removed.
With use of this structure, when the paper tray is pulled out from the paper feeding apparatus, the handling member is retreated from the paper feed roller to thereby be able to avoid its interference with the paper feed roller. Also, the mechanism for retreating the handling member can be simplified in structure.
In case where the paper tray is structured such that it can be removed by pulling out the same in the opposite direction to the paper feed-out direction, for a mechanism for bringing the sheets of paper stored in the paper tray into contact with the paper feed roller, there can be employed the following structure:
That is, a paper feeding apparatus comprises: a paper tray in which sheets of paper are piled up and stored; and, a paper feed roller contactable with the upper surfaces of the sheets of paper stored in the paper tray to feed out the sheets of paper one by one from the paper tray, wherein the paper tray can be removed from the main body of the paper feeding apparatus supporting the paper feed roller by pulling out the paper tray in the opposite direction to the paper feed-out direction; the paper tray includes a paper carrier plate disposed on the bottom portion thereof, and a pull-up member connected to the paper carrier plate for pulling up the paper carrier plate to a position where sheets of paper on the paper carrier plate can be contacted with the paper feed roller; and, on the main body of the paper feeding apparatus into which the present paper tray can be removably mounted, there is further mounted a guide member engageable with the pull-up member to thereby guide the pull-up member upwardly in linking with the inserting or mounting operation of the paper tray.
And, the guide member includes two guide surfaces, while the two engagement portions of the pull-up member can be engaged with the present two guide surfaces sequentially and the pull-up member can be thereby pulled up in two stages.
According to this structure, when the paper tray is inserted into the apparatus main body, the paper carrier plate disposed on the bottom portion of the paper tray is pulled up to thereby be able to bring the upper surface of the paper stored in the paper tray into contact with the paper feed roller. The sheets of paper piled up on the paper carrier plate vary in quantity according to replenishment or consumption thereof. However, the pull-up member is guided by the two guide surfaces of the guide member and is thereby operated in a large range so that the sheets of paper can be properly contacted with the paper feed roller regardless of the quantity of the sheets of paper to be stored. Also, as a pull-up member, there can be disposed a member having sufficient strength in a narrow space and thus, even in case where a large number of sheets of paper are stored in the paper tray and the weight of the sheets of paper is large, the pull-up member is able to operate the paper carrier plate.
By the way, the mechanism for retreating the handling member from the paper feed roller and the mechanism for bringing the sheets of paper on the paper carrier plate into contact with the paper feed roller are not limited to the paper feeding apparatus or image forming apparatus including two or more paper feed rollers, but these mechanisms can also be applied to an apparatus including one paper tray and one paper feed roller as well as to other various types of apparatus.